He staked Todd Combs and Ted Weschler with $1.75 billion each and allowed them to make their own stock selections. Combs came on board in early 2011; Weschler, at the start of this year. Both had reputations for beating the market, and Combs did well in his first year at Berkshire (ticker: BRK.A).

So, what have the two been buying? It's hard to know for certain, but given Buffett's comments in Berkshire's 2011 annual report, and the boss's predilection for focusing on multibillion-dollar investments, it's logical to assume that purchases in the $200 million to $400 million range cited in company filings reflect decisions made by Combs and Weschler.

The table below highlights Berkshire holdings that could be in their portfolios. Based on the timing of each purchase, we have speculated about whose portfolio each stock resides in. Positions initiated in 2011 likely were established by Combs; this year's purchases probably are Weschler's. Neither would comment.

WESCHLER OWNED DAVITA, a leading provider of kidney-dialysis services, DirecTV, and Liberty at his prior job managing Peninsula Capital Advisors. All are large Berkshire positions, which could mean they are owned by both managers, and possibly, Buffett. Combs and Weschler supposedly share ideas; both are eligible for bonuses, with 80% keyed to individual performance and 20% based on how well the other does.